Why the Pablo Neruda 'poisoning' saga rolls on

Toxicology tests appear to have conclusively proved that the Chilean poet died of natural causes – but his driver and some of his family are demanding further investigation, maintaining he was murdered by the Pinochet regime

Members of Pablo Neruda's family are contesting toxicology reports on the exhumed body of Chile's most famous poet that appeared to reveal he was not assassinated, as many have believed since his death in 1973.

After seven months of forensic tests, it was announced on 8 November that no signs of poison had been found in the remains of Neruda – the man Gabriel García Márquez called "the greatest poet of the 20th century in any language". Yet some of Neruda's family are not satisfied and have asked for the examination of the body to continue.

Neruda died at the age of 69 on 23 September 1973, just 12 days after Augusto Pinochet's military coup. His body was exhumed from home at Isla Negra, on Chile's Pacific coast, on 8 April 2013 following claims by the poet's driver, Manuel Araya. He maintains that, although Neruda was suffering from prostate cancer, his illness was under control and his death was accelerated on the orders of the Pinochet junta by an injection in his stomach as he lay in his hospital bed in Santiago.

It is known that Neruda had been offered safe passage out of Chile to Mexico on 22 September by the Mexican ambassador, Gonzalo Martínez Corbalá. Araya insists that the poet was murdered the following day to prevent him from fleeing into exile where, as a world-renowned member of the Chilean Communist party, he would have presented a powerful voice of opposition to the Pinochet regime.

For more than half of this year, 15 forensic scientists in Chile, North Carolina in the United States and Murcia in Spain examined Neruda's remains, seeking any indication of toxins. On 8 November, Dr Patricio Bustos, director of the Chilean forensic service, the Servicio Médico Legal, announced: "No relevant chemical agents were found besides the pharmacological chemicals used at that time for prostate cancer. Pablo Neruda died of natural causes, due to his prostate cancer."

Neruda's family is divided. One of his nephews, Rodolfo Reyes, is unconvinced by the forensic findings. He cited a report released on 6 November by a Swiss laboratory on the remains of the Palestinian leader, Yasser Arafat, indicating results consistent with polonium poisoning. "We have to keep investigating," said Reyes. "This is just the start."

He added that he would ask Mario Carroza, the Chilean judge in charge of the case, for further biological tests for traces of sarin gas and thallium. "The judge has said he is open to that possibility," Reyes said. "This report does not mean that the criminal investigation into the death will be closed, and there is enough reasonable doubt that merits keeping it open."

In stark contrast, another of Neruda's nephews, Bernardo Reyes, is certain that Neruda died of natural causes. "All the speculation merely discredits its authors. It sprang from the mind of a man [Araya] guilty of thousands of contradictions, and he has been aided and abetted by journalists prone to sensationalism rather than any desire for objectivity."

So, four decades after his death, 1971 Nobel prize winner Neruda remains at the centre of a continuing intrigue. Indeed, the story took a bizarre new twist in late July this year, when Attorney Eduardo Contreras, who represents Chile's Communist party, requested further tests to confirm whether the remains being examined were actually those of Pablo Neruda at all. Contreras pointed out that this was the third time Neruda's body had been exhumed: he had previously been moved to the General Cemetery in Santiago in 1974, then for a second time in 1992 to be buried at Isla Negra.

Contreras added: "The fact should not be ignored that the dictatorship, in order to avoid the discovery of thousands of crimes, hid bodies, changed the locations of remains, buried others in their place, threw bodies into the sea, burned others." Judge Mario Carroza agreed to allow these tests, adding that, if necessary, the DNA of the remains would be compared with that of Neruda's parents, who are buried in southern Chile.

Araya appears to be totally unpersuaded by the forensic report. In an interview, he declared: "After more than 400 tests on his remains, they were unable to say what Pablo Neruda died of. It's ridiculous. They need to do more investigations, and the judge is going to order these. We are sure he was murdered, because he was not close to death."

For his part, Carroza told journalists that it was still impossible to state with certainty whether Neruda was murdered or not: "This will take more time." One of the scientists involved in the tests on Neruda's remains, Spain's Francisco Etxeberría – who also took part in the exhumations of Chile's President Salvador Allende, toppled by the Pinochet coup, and the murdered Chilean singer-songwriter Víctor Jara – said: "We didn't find any forensic evidence indicating that [Neruda's] death was not a natural one." Nevertheless, he conceded that analysis of bone, especially after four decades, was much more difficult than testing a recently deceased body.

Meanwhile, Contreras also called for more tests on Neruda's remains. "Toxicological tests must be performed before any conclusive analysis results seal the case. We are going to request more samples because, even though they apparently did not find chemical agents, they never studied biological agents. A very important chapter has closed, but this is not over." Araya's contention that Neruda was not in a critical condition at the time of his death is contradicted by some of the friends who visited him in Room 406 of the Santa María Clinic in Santiago in the last days of his life. They told me they found him extremely ill.

Others, however, claimed that he was lucid, pointing out that he was continuing to dictate his memoirs to his secretary, Homero Arce. Neruda's widow, Matilde Urrutia, always maintained that his cancer was under control. It seems clear to many that the poet's condition was exacerbated by his torment over the horrors being committed by Pinochet's agents.

The day after Neruda's death, the Chilean daily El Mercurio published a story stating that the poet had died as the result of shock brought on after an injection. This version disappeared completely from the official diagnosis, which was malnutrition and wasting away related to his prostate cancer. However, the official hospital medical records relating to Neruda's death have also vanished, adding to the mystery.

On 31 May this year, Carroza issued an order for the police to track down a certain Dr Price – the man said to have been treating Neruda to the end. Although there is no record of a Dr Price in any of the hospital's archives, the description of Price as tall and blond with blue eyes is reported to match that of Michael Townley, a CIA double agent who worked with the Chilean secret police under Pinochet. Townley was put into the witness-protection programme after he admitted killing critics of Pinochet in Washington and Buenos Aires. At the beginning of June this year, US sources insisted that Townley had not been in Chile on the day Neruda died.

Those maintaining that Neruda may have been murdered also point to the fact that Eduardo Frei Montalva, president of Chile from 1964 to 1970, died in the same Santiago hospital, the Santa María Clinic, in 1982 after expressing his opposition to the military dictatorship. Frei's death was initially attributed to septic shock during a routine operation, but a 2006 investigation proved that he had been assassinated with mustard gas and thallium.

Asked why it was so important to determine precisely how Neruda died, the Chilean writer Antonio Skármeta said he still believed Neruda died of cancer. "Yet there is legitimate doubt … The whole affair is extremely sad, especially the removal of Neruda's remains from his beloved home at Isla Negra. But Chile needs to know for certain what actually happened and [if he was murdered], the criminals have to be tracked down."